1. Field of the Invention
The present invention is directed to vibratory separators, screen-supporting baskets for them, and, in certain particular embodiments, to shale shakers for treating drilling fluid, screen-supporting baskets for them, screens for such separators and shakers and methods of using such screens, shakers, baskets, and separators.
2. Description of Related Art
Vibratory separators are used in a wide variety of industries to separate materials such as liquids from solids or solids from solids. Typically such separators have a basket mounted in or over a receiving receptacle and vibrating apparatus for vibrating the basket. One or more screens is mounted in the basket. Material to be treated is introduced to the screen(s). Separated material (e.g. liquid and/or smaller solids) flows through the screen(s) into the lower receptacle and separated larger solids (with or without liquid) move down and off the screen(s).
The need for solids control in drilling fluid or xe2x80x9cmudxe2x80x9d used in hydrocarbon well drilling is well known in the prior art. Drilling mud, typically a mixture of clay and water and various additives, is pumped down through a hollow drill string (pipe, drill collar, bit, etc.) into a well being drilled and exits through holes in a drillbit. The mud picks up cuttings (rock) and other solids from the well and carries them upwardly away from the bit and out of the well in a space between the well walls and the drill string. At the top of the well, the solids-laden mud is discharged over a shale shaker, a device which typically has one or a series of screens arranged in tiered or flat disposition with respect to each other. The prior art discloses a wide variety of vibrating screens, devices which use them, shale shakers, and screens for shale shakers. The screens catch and remove solids from the mud as the mud passes through them. If drilled solids are not removed from the mud used during the drilling operation, recirculation of the drilled solids can create weight, viscosity, and gel problems in the mud, as well as increasing wear on mud pumps and other mechanical equipment used for drilling.
Typically, the screens used with shale shakers are emplaced in a generally horizontal fashion on a generally horizontal bed or support within a basket in the shaker. The screens themselves may be flat or nearly flat (i.e. substantially two-dimensional); or, due to corrugated, depressed, or raised surfaces, are three-dimensional. The shaker imparts a rapidly reciprocating motion to the screen. Material from which particles are to be separated is poured onto a back end of the vibrating screen. The material generally flows toward the front end of the screen. Large particles are unable to move through the screen, remain on top of the screen, and move toward the front of the screen where they are collected. The smaller particles and fluid flow through the screen and collect in a bed, receptacle, or pan beneath the screen.
Referring now to FIG. 1, a prior art shale shaker 1 has a screen 2 (with screen or screening cloth or mesh as desired) mounted on vibratable screen mounting apparatus or xe2x80x9cbasketxe2x80x9d 3. The screen 2 may be any known screen or screens. The basket 3 is mounted on springs 4 (only two shown; two as shown are on the. opposite side) which are supported from a frame 6. The basket 3 is vibrated by a motor 5 and interconnected vibrating apparatus 8 which is mounted on the basket 3 for vibrating the basket and the screens. Elevator apparatus 7 provides for raising and lowering of the basket end. Typically the basket will be in a xe2x80x9cclimb the hillxe2x80x9d position (see FIG. 4) so that a pool 9 of liquid is maintained at one end within the basket.
FIG. 2 discloses one example of a typical prior art shaker system (e.g. as shown in U.S. Pat. No. 5,190,645). The system A has a shale shaker K having a screen or screens S. The screen(s) S are mounted in a typical shaker basket B and one or more vibrators V (any known suitable shaker vibrator) vibrate the basket B and hence the screen(s) S. The other components of the system A are as described in U.S. Pat. No. 5,190,645 incorporated fully herein for all purposes.
FIG. 3 shows schematically a prior art system C with a Mud Box (Back tank, Possum Belly) to distribute the flow to a screening surface. The screens are mounted in a Deck (Basket) which is vibrated to assist the throughput of mud and movement of separated solids. The deck rests on Vibration Isolation Members, such as helical springs or rubber mounts. The vibration isolation members rest on the support member, which is also used to divert flow as desired, and is called a Bed. There are many deck, basket configurations used depending on the design criteria. The deck, basket, may be flat, horizontal, or mounted at a slope.
On sloped deck units (e.g. cascade or parallel flow), the screens may be continuous with one screen covering the entire deck length, or have a divided deck which has more than one screen used to cover the screening surface, or with individual screens mounted at different slopes. On multiple deck units, more than one screen layer may be employed. In a two or three deck unit, the mud passes through one screen before flowing through the second.
The motion of the shaker controls the efficiency of separation, rate of travel of cuttings on the screen, solids separation capacity and fluid capacity. The shape and axial direction of the vibration motion along the deck is controlled by the position of the vibrator relative to the deck and the direction of rotation of the vibrator.
Shale shakers have capacity limits. Exceeding a capacity limit means excessive mud will be discharged over the ends along with the solids. Capacity limits are typically defined for non-blinded screens. Capacity limits of a shale shaker include:
1. The solids capacity limit is the maximum amount of solids that a device will remove; and
2. The liquid limitxe2x80x94the maximum GPM capacity for various drilling muds.
The solids capacity limit is encountered when drilling soft, gummy formations. Usually the liquid limit controls the minimum size screen that can be used for a given circulation rate. The thicker the mud, the lower the GPM capacity. Open area of the screens and usable area of the screening deck influence this limit. The solids capacity and/or liquid capacity varies with different shaker designs. In practice, the smallest screen size that can be employed without flooding a unit is used.
There is a need for an efficient vibratory separator system which is efficient and cost-effective with increased efficiency, and screen throughput.
The present invention discloses, in at least certain aspects, a screen-supporting basket for a shale shaker or other vibratory separator that includes two side walls spaced-apart and interconnected by an end wall at a first end. A second end has bracing, bars, or beams spacing-apart the side walls, the bracing etc. positioned so that an end of a screen is above it. One or more screens (any known in the art) for treating fluid introduced at the shaker""s first end are mounted in the basket in any way known in the art. The basket is mounted over a receptacle for receiving fluid and/or solids flowing through the screen(s).
The end wall at the first end of the basket has an opening therethrough. An upright end screen is emplaced over or in this opening so that liquid and/or solids in the material introduced into the basket may flow through this screen and into the receptacle below the basket. Such an end screen according to the present invention can be provided for any known basket when an end opening according to the present invention is provided in the basket""s end wall. Such an end opening may be any desired size or shape and can extend for only a portion or over substantially all of the end wall.
In one aspect the screen is releasably held in place over the end-wall opening by sliding it down into channel members on either side of the openings and blocking or wedging it in place. Any suitable seal or gasket or sealing material may be used on the screen, on the channels and opening edge, or on both to sealingly position the screen over the opening. Any other suitable method or structure may be used to releasably position and hold the end screen over the end opening, including, but not limited to, channels alone, nuts and bolts, clamps, glue or other adhesive, releasably cooperating fastener material such as VELCRO(copyright) material, or screws. Any known inflatable structure or bladder, or releasable tensioning bolts may be used to hold a screen in place. Alternatively the screen can be welded, soldered, or brazed at the openings edges. The end screen may be a single integral screen or multiple adjacent end-to-end screens may be used at the basket end. Also, multiple adjacent parallel vertical screens may be used positioned so that fluid from within the basket flows through all of them. Such vertically xe2x80x9cstackedxe2x80x9d screens may all be mounted within the basket; outside the basket; or one or more of them may be mounted within the basket and one or more of them mounted outside the basketxe2x80x94with appropriate mounting members, gaskets, seals, seal members, and/or bolts and nuts so that fluid flows through the screens and then exits from an outermost screen. Any screen disclosed herein as being in a vertical orientation within a basket and over a basket opening may be at an angle to the bottom of the basket; e.g., but not limited to in an orientation such that a top end of the screen contacts a portion of an end wall or a side wall and a bottom portion of the screen contacts a portion of the bottom of the basket. Also, such a screen may overlie part of a bottom screen.
In one aspect the end screen has a plate, mounting structure, or frame and with a lower part that is perforated or has holes or openings so that fluid flowing onto it flows through this part of the frame and out and down into the collection receptacle beneath the basket.
A shaker, in one embodiment according to the present invention, e.g. with basic components as the shaker in FIG. 1, is, according to the present invention, provided with a basket as described herein according to the present invention.
In other aspects one or both sides of a basket as described above according to the present invention also has one or more side screens through which fluid and/or solids from the material introduced into the basket can flow out and down into the receptacle below the basket. Optionally, there is no end screen as described above and only screen(s) on one or both side walls. Such side wall screens may be any as described above mounted in any way as described above for end screens.
In one basket according to the present invention a plurality of openings are provided on the side walls and end walls of the basket and, as desired, a screen may be used over any, some, or all the openings. For an opening not covered by a screen, a blocking plate or member is releasably and sealingly installed over the opening(s) to close off the opening to flow. According to the present invention one or more such screens may be installed within the basket on its interior over the opening or on the basket""s exterior surface over the opening. Alternatively, with appropriate holding devices, a screen according to the present invention may be sized to fit sealingly within an opening. Any known flat, substantially flat, two-dimensional or three-dimensional screen or screen assembly, appropriately sized and configured, may be used according to the present invention to close off one or more end and/or side basket openings.
A basket as described above according to the present invention provides more screening area to treat material and separate its components than a conventional basket with the same footprint. By thus increasing the available screening area, the load on the horizontal screen(s) is reduced; their efficiency, and productivity are increased; and total throughput for the basket is increased. Shaker or screen capacity is typically determined by the position of a xe2x80x9cfluid-end pointxe2x80x9d. The fluid end-point is the point where the fluid pool stops on the screen surface near the shaker""s discharge end. As the fluid-end point moves closer to the discharge end, discharged solids can become too wet, risking whole mud losses over the screen. A typical rule of thumb for optimum shaker capacity specifies covering 66% or less of the shaker""s screen surface. The integration of vertical screens into a shaker basket according to the present invention shortens the length of the fluid pool, effectively increasing shaker capacity.
Solid loading has as great an effect on shaker capacity as liquid volume. As solids take up screen area, liquid throughput is impeded due to the moving solids bed on the screen surface. The effect of heavy solids loading on screening capacity is exponential. Heavy solids loading creates a condition for fluid to ride on top of the moving solids bed, and creates conditions susceptible to whole mud losses. One solution to this problem has been to use coarser screens to prevent whole mud losses. This solution solves the immediate concern for the loss of whole mud, but may be at the expense of poor solids control.
The motion of the basket conveys solids away from the vertical screen(s) at the rear and/or sides of the shaker basket. Thus some portion of the fluid in the pool that exits through end and/or side basket screen(s) according to the present invention bypasses the traditional routing of prior art baskets, thereby enhancing shaker capacity.
Baskets according to the present invention with one or more screens according to the present invention enhance capacity, especially if there is enough flow to generate a pool on the screen surface. This is particularly true during heavy solids loading due to high penetration rates and large diameter hole conditions, or both.
In certain aspects, the end screen in a basket according to the present invention is at such an angle to the direction of the force of strokes of the vibrating apparatus that separation is enhanced as compared to the angle of these strokes with respect to the horizontal screen(s).
When a basket in a shaker has one elevated end (as shown in FIG. 4) so that the separated solids run xe2x80x9cuphillxe2x80x9d, liquid is prevented from running off the screen""s exit end; and a pool of liquid is formed at the basket""s opposite endxe2x80x94by using an end wall opening(s) and screen(s) and/or appropriately located side wall opening(s) and screen(s) a portion of this liquid (and perhaps some small separated solids) flows out from the basket through the end screen(s) and/or side screen(s) and the horizontal screen(s) in the basket beyond the pool are not impacted by and do not have to process this portion of the liquid that flows out through the end screen(s) and/or side screen(s). Optionally, part or all of a basket""s floor may be closed off to flow rather than completely or substantially completely covered with screen(s). In one aspect part of all of the area beneath a pool formed in a basket is closed off to flow and side and/or end screens treat the pool material.
The present invention, in one embodiment includes a shale shaker with a frame; a xe2x80x9cbasketxe2x80x9d or screen mounting apparatus in the frame; one or more screens positioned in a flat position in the basket; basket vibrating apparatus; one or more end basket screens and/or one or more side basket screens; and a collection tank or receptacle below the basket. In one particular aspect such a shale shaker treats drilling fluid.
In certain embodiments the present invention discloses a screen mounting basket for a vibratory separator for separating components of material introduced into the basket, the vibratory separator including a collection receptacle beneath the basket, the basket with two opposed spaced-apart side walls having first ends and second ends, the first ends spaced-apart by an end wall connected to each of the side walls, a basket bottom opening between the two spaced-apart side walls, basket bottom screening apparatus at the basket bottom opening, at least one basket aperture not through the basket bottom, at least one aperture screen over the at least one basket aperture, and the at least one aperture screen and the bottom screening apparatus for separating a component material from the material introduced into the basket, material flowing through the at least one aperture screen not flowing through the bottom screening apparatus, the separated component material flowing into the collection receptacle.
The present invention discloses, in certain aspects a screen apparatus for a vibratory separator, the vibratory separator having a basket, the vibratory separator for separating components of material introduced into the basket, the vibratory separator including a collection receptacle beneath the basket, the screen apparatus including screening material, a support, the screening material on the support, the support having a plurality of openings therethrough suitable for the flow of fluid therethrough, the fluid from the material introduced into the basket, the support having a plurality of fluid conducting channels therein at an angle to the plurality of openings so that fluid flowing into one of the plurality of openings may then flow into one of the plurality of fluid conducting channels and out from the support into the receptacle. In one aspect a screen assembly with such a support (e.g. a frame or a plate) is stood on end at an end or side basket opening.
The present invention discloses, in certain aspects, a vibratory separator system for separating components from a liquid-solid mixture fed to the vibratory separator system, the vibratory separator system with a frame, a screen mounting basket on the frame, vibrating apparatus connected to the screen mounting basket for vibrating the screen mounting basket, the screen mounting basket like any described herein according to the present invention.
The present invention discloses, in certain aspects, a method for reducing the weight of material on the bottom screening apparatus of a vibratory separator, the vibratory separator having a screen mounting basket into which the material is introduced, the vibratory separator including a collection receptacle beneath the basket, the basket with a plurality of interconnected walls, a basket bottom opening between the walls, basket bottom screening apparatus at the basket bottom opening, at least one basket aperture through one of the walls and not through the basket bottom, at least one aperture screen over the at least one basket aperture, and the at least one aperture screen and the bottom screening apparatus for separating a component material from the material introduced into the basket, the separated component material flowing into the collection receptacle, the method including introducing the material into the basket, flowing part of the material through the at least one aperture screen, said part flowing into the receptacle without passing through the bottom screening apparatus.
It is, therefore, an object of at least certain preferred embodiments of the present invention to provide:
New, useful, unique, efficient, non-obvious baskets for vibratory separators and shale shakers and methods for using them to separate components of material to be treated thereby.
Such baskets with one or more end wall openings with one or more end wall screens for treating material; and/or with one or more side wall openings with one or more side wall screens for treating material;
Such a basket which provides for a pool on top of a topmost screening layer that has a pool end boundary that is relatively further away from a discharge end of a shaker as compared to such pools in prior art shakers or vibratory separators;
Such a shaker with any such basket; and
A system with any such basket that has relatively increased throughput and which increases screen life.
The present invention recognizes and addresses the previously-mentioned problems and long-felt needs and provides a solution to those problems and a satisfactory meeting of those needs in its various possible embodiments and equivalents thereof. To one of skill in this art who has the benefits of this invention""s realizations, teachings, disclosures, and suggestions, other purposes and advantages will be appreciated from the following description of preferred embodiments, given for the purpose of disclosure, when taken in conjunction with the accompanying drawings. The detail in these descriptions is not intended to thwart this patent""s object to claim this invention no matter how others may later disguise it by variations in form or additions of further improvements.